Sprinting animation

I have this script for sprinting and crouching and I want it to play a sprinting animation when you hold shift. but it doesn't play the animation and I clip through the floor when I press shift.

     var walkSpeed : float = 7; //Regular speed
     var crouchSpeed : float = 3; //Speed while crouching
     var sprintSpeed : float = 13; // Speed while sprinting
     
     private var charMotor : CharacterMotor;
     private var charController : CharacterController;
     private var theTransform : Transform;
     private var charHeight : float; //Initial height
     
     function Start () 
     {
         charMotor = GetComponent(CharacterMotor);
         theTransform = transform;
         charController = GetComponent(CharacterController);
         charHeight = charController.height;
     }
     
     function Update () 
     {
         var h = charHeight;
         var speed = walkSpeed;
         
         if (charController.isGrounded && Input.GetKey("left shift") || Input.GetKey("right shift"))
         {
             speed = sprintSpeed;
             animation.Play("camRun");
             
         }
         
         if (Input.GetKey("c"))
         {
             h = charHeight*0.5;
             speed = crouchSpeed;
         }
         
         charMotor.movement.maxForwardSpeed = speed; // Setting the max speed
         var lastHeight = charController.height; //Stand up/crouch smoothly
         charController.height = Mathf.Lerp(charController.height, h, 5*Time.deltaTime);
         theTransform.position.y += (charController.height-lastHeight)/2; //Fix vertical position
     }